Method of producing puffed pulp



June 7, 1933 J. E. PLUMSTEAD Re. 20,752

METHOD 0F PRODUCINGrl PUFFED PULP Original Filed May 9, 1929 2 Sheets-Sheet l @fg-1 N Ha PULP. PuFF//va ope/PA/o/v Reuued June 7, 1938 PATENT vOFFICE METHOD F PRODUCING PUFFED PULP Joseph E,\Plumstead,'wilmington, Del., assignor, by mesne assignments, to The Jessup & Moore v Paper Co., Maryland Original No. 1,830,131,

Serial No. 361,708, May 9, 1929. for reissue March 23, 1933, Serial 2s claims. This invention relates to the production of puffed pulp, particularly adapted for use in the manufacture of sheet material on a paper making'machine. y One of the objects of the invention is the' production in an economical way of putl'ed pulp, which will exhibit a maximum percentage of curled bers and contain a minimum amount of deleterious material.

Another object of the invention is to so combine the soda process of producing pulp and recovering. the valuable portions of the liquor drained and washed from the puiiing method, as to eiect a nomical operation.

Theinvention primarily involves subjecting the substantially dry pulp to impregnation by a strong caustic solutionin a suitable-impregnator, wherein the liquid content of the mass will be limited in amount so that the mass will be maintained in a non-fluid condition. f

'Further objects of the invention will appear, as the same is particularly described hereinafter. The invention will be hereinafter described in g5 connection with the 'accompanying drawings, in

which Fig. 1 shows diagrammatically a soda process.

Fig. 2 shows diagrammatically one exemplifies,- tion of my pulp pulng procedure.

Fig. 3 shows diagrammatically one exempliiication of a combination of the soda process ,with the puiing procedure, and

Fig. 4 shows conventionally a type Aof impregnator which can be used in the puillng operation, and means for supplying a causticsolution of regulated concentration to same.

particularly ecol5 Referring to Fig. 1, 5 designates a tank ior receiving the caustic soda liquor of the desired concentration, or strength, for use in the cooking operation which is carried on in a digester, not shown.

'I'he residue of colored liquor drained and washed "from the cookedpulp is treated in aA furnace designated 6 and the black ash formed is then treated in leachers designated 1. 'I'he resultant carbon is discharged from the system and the soda ash solution with the wash water and-condensed steam is then discharged in a causticizing pan, designated 8, where it reacts 0 with reburned lime `to form a first caustic alkali of approximately the highest strength which wili permit the desired reaction to proceed, say, for example.- 16% sodium hydroxide (NaOH)` conl centration.

The clear solution is decanted and discharged pulp, with my pulpv Philadelphia, Pa., a corporation of dated November 3, 1931, Application No. 66.".365V

(Cl. liz-13) ai'ter dilution, as will be hereinafter described, into the tank 5. 'Ihe residue, as shown in Fig. 1, passes to a second causticizing pan 8a, into which is discharged the decanted sodium hydroxide from pan 8b andvcaustic soda iiltrate from lime iilter 9. f

'I'he decanted sodiuin hydroxide in pan 8a, which would be somewhat less than half the strength of that discharged from pan 8 (say, for example, approximately '7% concentration), is discharged into tank 5, and serves for diluting the sodium hydroxide discharged from tank 8, as previously described.

The residue from tank 8a is discharged into causticizingpan 8b, to which additional water is supplied. The sodium hydroxide decanted in this pan is discharged into pan 8a.

'Ihe residue from pan-8b is passed to a lime iilter 9, which is supplied with a suitable quantity of water to recover the last traces of sodium hydroxide, which is passed to the pan 8a.

The residue from the lime nlter is passed to a lime recovery plant. and the reburned lime therefrom is supplied to the first causticizing pan 8.

`As will be observed, the solution of sodium hydroxide which is used for the cooking operation carried on in the digester consists` of the liquor from the causticizing pan 8, of approximately 16% concentration, and the liquor from the Icausticizing pan 8a, having approximately 7% concentration, so that the solution used 'in the digester has approximately a 10% concentration. The volume of clear caustic solution discharged from pan 8a is in volume somewhat greater than that discharged from pan 8, due to the denser settling of the carbonate sludge in the weake caustic solution.

It will be understood that the procedure so far described constitutesA no part of myy invention. I One exemplilcation of that part of my invention relating to pulling pulp by impregnating the same with a strong caustic solution is shown diagrammatically in Fig. 2, to-which reference is now made.

In practicing this exemplification of my invention, 4substantially dry fibrous cellulose pulp, or raw material is delivered to an impregnating vkneader I to which 'is also delivered caustic alkali solution of suilcient strength, say 7% to 24%, to cause a curling of the libres of the pulp upon impregnation. 'I'he caustic alkaliv is added only in such quantities that a resultant substantially non-fluid mass will be produced, the mass containing at least 10% oi.' fibrous material, the realkali solution.

lThe impregnating kneader may consistl oi aY Lannoye pulper or any suitable kneader, such as shown in Fig. 4 in which the pressure producing means comprises the weighted valve A- and the caustic strength varying means comprises separate valved conduits for water and caustic leading to a mixing chamber B which feeds the kneader, in case it is desired to vary the strength of the caustic fed to the kneader.

The purpose oi the impregnation is to cause the curling of the libre of the cellulosic pulp mass and a swelling, or puihng, of such mass so that a highly absorbent sheet of felt material may subsequently be produced from the puii'ed pulp by a paper making machine.

Exposure to or contact with air is entirely unnecessary in the puffing, or curling of the bres of the cellulose mass. y 'Ihe puiling takes place upon contact ofthe individual ilbres with the strong causticsolution, regardless of the presence or .absence ot air in contact with the iibre. This pulling is not demonstrated. or apparent, however, until after thorough washing out of all caustic and dissolved substances, such as slimy hemi-cellulose or cementitious substances. In fact, it is probably better not to expose the ilbre and solution to the air before washing. The caustic liquor may be said to have a mercerizlng effect on the individual nbres which causes a swelling of the bre casing and a skin tension unevenly distributed which causes the fibre to curl.

The treatment o! the cellulosic iibrous material with caustic soda results also in a dissolvingof the hemi-celluloses which are those carbohydrates which are insoluble in water but soluble in dilute lacids and alkalis. The dissolving ofthe hemi-celluloses causes a consequent increase in the highly resistant alpha-cellulose percentage of the ilnished product, thus accomplishing cellulose puriilcation. y

It is desirable to@ entirely flll the pulper or kneader with the mass of pulp and caustic and to deliver the material thereto in such quantity that the mass of material and caustic alkali by reason of weighted outlet valve A (Fig. 4), will be under pressure which will aid in the quicker impregnation of the fibrous mass with the sodium hydroxide solution.

It is also desirable to provide for varying the` strength of the sodium hydroxide solution by mixing means B (Fig. 4), to compensate for variations in the moisturecontent of the substantially dry cellulosic material being treated.

The pulp and caustic, after passing through the pulper or kneader, is then preferably passed to dehydrator la where the' mass is wrung` or pressed .to remove some of the strong treating caustic solution therefrom and to reuse the recovered strong solution in the impregnation in the kneader.

The mass of puii'ed or purified pulp and caustic as shown in Fig. 2 is then preferably passed into an agitator tank 2 where more sodium hydroxide solution of weaker concentration is addedA causing the puiled pulp to become thoroughly impregnated and to be made iluid and of less consistency. The pulp and caustic is then transferred to a dehydrator 3 where it is dehydrated and the caustic solutionv is withdrawn, the pulp then being passed to a washer l in which residual caustic is removed by washing the purified or puffed pulp with water. The caustic solution Escasa tothe impregnating kneader and reused in the `means of a suitable paper making machine, not

n plishment of this advantageous use and distribulwhich may or may not be fortied by stronger the lime iliter or sludge waslier.

withdrawn from dehydrator l may be returned manner described with respect to dehydrator la. The washed pulled pulp is then ready for formation into sheets of highly absorbent felt by shown.

, Fig. 3 is a flow sheet showing a method of combining the process of pulling the pulp shown in Fig. 2, with the process of the preparation oi thecaustic alkali in the operation of a soda pulp mill as shown in Fig. 1. According to the process of Fig. 3, the caustic alkali used in the putllng operation is reused. in the regular pulp cooking operation without any unusual dilution of the alkali solutions. It is important to the accomtion -of caustic alkali without dilution, that substantially dry pulp be used at the start of the pufllng operation. The pulpformed in the digesters is therefore substantiallyv dehydrated after washing the black liquor therefrom, prior to starting the puiling operation.

Of course, other pulps may be used than that produced from caustic soda.

The combining of the pufilng operation with the operation of the sodapulp mill is accomplished according to the present invention by pumping a portion of the strong (say about 16%), caustic liquor from ycausticizing pan B caustic, to the Lannoye pulper or impregnating kneader I, the other portion going to the digester strength solution tank 5 as before. The second liquor from pan 8a instead oi passing directly to the digester solution receptacle 5 is passed directly to the agitator tank 2, and reaches the tank 5 indirectly ,after aiding in the pulling operation and passing through agitator tank 2 and dehydrator 3. The strong treating solution from the kneader also reaches the tank 5 after passing through dehydrator la, tank 2, and dehydrator l.

A portion of the third liquor from pan 8b and the weak dilute solution fromthe lime filter .returns to pan la as before, while a portion thereof passes to agitator tank 2 with the second solution from pan Ba, through the dehydrator to tank 5.

A further portion of the weakest solutions (third liquor and lime filter solutions), is pumped directly to the tank 5.

A very weak caustic solution is obtained in the residual caustic washer I and this solution is conveyed in part to lime filter 9 and in part to pan 8b. i

It will thus be seen that the present invention provides a novel pulp puffing process combined with a soda pulp mill caustic recovery and pulp cooking process so as to conserve without substantial dilution, the caustic liquors used in' both the pulp cooking and puing operations.

From the foregoing description of my invention, it will be understood that the cellulose material is cooked in the usual digesters into which is discharged the caustic liquor from the tank 5 and that the caustic yis recovered in a lime caustic recovery system to a strength Within.` amercerizin-g activity range. This system includes As stated, the cooked pulp is treated in the mixing apparatus l, preferably aLannoye pulper.

with the recovered caustic, and the material therein has a pulp consistency not less than v1(l%-the mass containing 10%'of pulp` and the remainder being caustic soda and caustic alkali solutions.

Patent is:

is discharged into either, or both, of the pan 8b land lime filter 9.

It will be apparent that ymodifications may be made within the scope of the present invention and I do not desire to limit the invention to the exact steps shownin the iiow sheets, nor to the strengths of solution which are stated merelyby way of example.

The process of my invention is very rapid in its treatment of the pulp to puff the fibres and may require as low as one-hall? to three-quarters of apound of alkali per pound of pulp material treated.

It will be understood that I do not coniine my fibre treatment to fibres produced by any particular method but may use as a raw material fibres produced by the soda, sulphate, or sulphite processes, either cooked or uncooked cotton fibres, reed, grass, or straw cellulosic material, which may or may not have been previously bleached.

The continuous feature of the methods as referred to yin the 'specicatio'n and claims is intended to broadly refer to substantialcontinuity, as' it will be apparent that the process can be carried out more or less intermittently.

While it is specified that a substantially nonfiuid mass is produced in the pulp pulling operation, it is not desired to restrict the invention to effecting dilution after the mass has been discharged from the pulper or kneader, since it will be apparent that the dilution' of the non-fluid completely puffed m'ass could be readily effected in the pulper or kneader after the noir-fluid mass is formed, without departing from the scope` of the invention.

It is also not desired to limit the inventionto any particular diluting liquid.

What I claim and desire to protect by Letters l. 'I'he method of utilizing vthe caustic alkali solution of a soda pulp mill in producing pulled pulp including the steps of supplying to an impregnating kneader for the pulp a portion of the strong caustic solution from the first causticiz ing pan, the other portion passing to the supply of caustic alkali solution for cooking the wood pulp, conveying the puied pulp and caustic from the kneader to an agitating tank, conveying a second caustic liquor from a second causticizing pan to the agitator tank, conveying a portion .of a third and fourth caustic liquor from a third causticizing pan and from a lime filter to said agitator tank, another portion of said third and fourth liquors passing lto the second causticizing pan, conveying the puffed puriiied and agitated pulp and caustic to a dehydrator and conveying the caustic solution from' said dehydrator to said pulp cooking supply.

2. A method according to claim l including the step of passing a still further portion of said third and fourth liquors directly to said pulp cooking supply.

3. A method according to claim lfinoluding the steps of washing the puec'l pulp in a residual caustic washer and conveying the weak caustic thus obtained, in part to the third liquor and in part to the fourthliquor.

4. The continuous method of utilizing and economically conserving and reusing caustic alkali liquor for pulp cooking and for pulp puiing including the steps of delivering lto a pulper a portion of the strong caustic liquor from the first causticizing pan, delivering the other portion to the supply oi' caustic for cooking the wood pulp, conveying the puffed pulp and caustic from the pulper to an agitating tank, conveying a second and weaker caustic liquor from a second causticizing pan to the agitator tank, conveying a portion of a third and fourth caustic liquor from a third causticizing pan and from a lime filter t said agitator tank, conveying anotherportion of said third and fourth caustic liquors to the second causticizing pan, conveying a still further portion of said third and fourth liquors directly to said pulp cooking supply, delivering the puied and agitated pulp and caustic from the agitator to a dehydrator, conveying the caustic solution from said dehydrator to said pulp cooking supply, delivering the puffed pulp. from said dehydrator to a residual causticl washer, washing the puffed pulp and conveying the weak caustic solution thus obtained, in part to the third liquor and in part to' the fourth liquor.

5. The method of producing puffed pulp material comprising delivering substantially dry cellulosic fibrous pulp to` an impre'gnating kneader, delivering caustic alkali vto said impregnating kneader to produce in the kneader a pufiing or curling of the b'res and to produce a substantially non-fluid mass, delivering said non- `fluid mass to an agitator tank, delivering weaker lcaustic alkali to said agitator for further treatment of said mass, delivering said mass to a. dehydrator, delivering the dehydrated mass to a residual caustic Washer, and delivering the washed puffed fibrous pulp to a paper making machine and forming it into sheets ofhighly ab sorbent felt material.

6. The method of claim 5 in which the substantially dryr cellulosic material is delivered to said kneader and maintained under pressure therein substantially out of contact with air, and in which the caustic alkali is supplied in such uniform quantity as to maintain the mass inthe kneader over consistency, and slightly varying the concentration of the uniform volume of the caustic alkali as to compensate for any varlation in the moisture content of the substantially dry material supplied to the kneader.

'1. The method of claim 5 in which the mass is partially dehydrated upon delivery from the impregnating kneader and prior to delivery to -the agitator tank, the portion of strong caustic solution thus recovered being returned to the impregnator for reuse.

8. The method of claim 5 including the step of returning the caustic solution delivered from .said dehydrator to `said impregna'ting kneader for reuse. L 9. The method oi' claim 5 including the addi-L tional'steps of partially dehydrating the mass upon delivery from the impregnating kneader and prior to delivery to the agitator, returning the portion of strong caustic thus recovered to theimpregnator for reuse, and also returning to theimpregnator the caustic solution delivered from the dehydrator which follows the agitator.

10. The method of claim 5 in which the sub- Y stantially dry cellulosic material is delivered to said kneader and maintained under pressure therein.

11`. The method of claim 4 including the step of dehydratingv the puffed lpulp and caustic mass pnor to its delivery@V the aglutina mix ma returning the thus recovered portion ci' strong treating caustic solution to the puiper for reuse. 12. The hereindescribed method of producing I puffed pulp including treating substantially dry cellulosic fibrous pulp material ina kneader with caustic alkali solution of suillcient strength such as will produce a pulling of the pulp or curling of the fibres and in such volume of solution as to produce a resultant substantially non-.fluid mass containing at least 10% of fibrous material, said resultant non-fluid mass as treated being of such density that there can be.no free drainage,

and washing the material substantially iree from caustic alkali and saponiiled substances.

13. The method of producing puii'ed pulp matey rial according to claim 12 including delwdrat.-

the pufl'ed fibrous non-fluidY mass and forming it into sheets of highly absorbent fibrous felt material. n

14. `The method of cooking and puinng pulp comprising substantially continuously delivering caustic alkali liquor to digesters for cooking pulp and substantially continuously delivering a portion of the same supply of caustic alkali to an impregnating kneader, treating substantially pulpconsisting in impregnating the substantially dry pulp with a caustic alkali solution of approximately 16% concentration in 'an impregnator, and maintaining the liquid content of the mass in such limited amount that it will not exceed 'that required for vproducing a non-uid mass.

20. A step in the method of producing puffed pulp by curling the bers thereof, this step consisting in impregnating the substantially dry pulp with a caustic alkali solution, and maintaining the fluid content of the mass of pulp and solution in such limited amount that it will not exceed that required for producing a non-iiuid mass.

21. A process for producing puffed pulp which comprises making paper pulp by cooking wood` chips in a, pulp digester with caustic soda, and washing the pulp. passing a mixture of the pulp thusproduced with caustic soda solution of mercerizing activity at a pulp consistency over 10% through' a mixing apparatus,` separating the caustic from the pulp, and returning the separated caustic to the pulp digester.

22. A process for producing puffed pulp which comprises cooking cellulose material with caustic soda. for the manufacture of paper pulp', re-

dry cellulosic fibrous pulp in said impregnating kneader with said caustic' alkali to produce a substantially non-fluid mass of puied bres, and' delivering a substantial portion of the caustic alkali used in the pufilng operation to the digesters for cooking pulp.

15. The method according to'claim 14 including the steps of purifying the puffed nbrous pulp, and

covering the caustic with a lime caustic recovery system to a strength within the range of mercerizing activity, treating paper pulp in a mixing apparatus with the recovered caustic at a pulp consistency above 1 0%, and. washing out the delivering the purified puffed fibrous pulp to a paper making machine and forming it into sheets of highly absorbent felt material.

16. The method oi cooking and pulling pulp comprising substantially continuously delivering caustic alkali liquor to digesters for cooking pulp and substantially continuously deliveringaI por-- tion of the same supply of caustic alkali to an' impregnating kneader, treating cellulosic brous caustic alkali yto produce a mass of puii'ed bres. andedelivering a substantial portion of the caustic alkali used in the puffing operation to the digesters for cooking pulp.`

A 17. The method of cooking and pullingpulp comprising continuously or intermittently de.

livering caustic alkali liquor to digesters for cooking pulp and continuously or intermittently delivering a portion oi.' the same supply of caustic alkali to an impregnating kneader in which is being treated a, brous cellulosic material in a substantially non-fluid condition to which the caustic alkali has been added when said cellulosic material is in a substantially dry state, and returning ay substantial portion of the caustic alkali used in the puffing operation for subsequent pulp cooking operations in the digesters.

18. The method of producing puffed pulp material according to claim- 12 including diluting the puiiled iibrous non-fluid mass, and subsequently dehydrating the diluted mass.

19. A step in the method of producing pulled out the caustic alkali.

pulp in said impregnating kneader with said.-

caustic. v

23. A processfor producing puffed pulp which comprises passing a mixture of paper pulp with caustic soda solution of mercerizing activity while maintaining a non-fluid pulp consistency over 10% through an impregnator, then subjecting the pulp to dehydration, thereafter treating it in an agitator tank with a caustic solution, then again subjecting the material to dehydration, and

thereafter treating the material in -a residual caustic washer.

24'. yA process for producing puied pulp which comprises passing a mixture of cellulosic fibrous pulp and caustic alkali solution of mercerizing activity through a mixing apparatus while maintaining a non-fluid mass therein, and washing 25. The methodof producing puffed pulp including passing cellulosic fibrous pulp material and caustic alkali solution of-suf'ficient strength to produce a pufling of the pulp orcurling of the bres through a kneader, the pulp material and caustic alkali solution being supplied in such proportion throughout the treatment that the material passing through the kneader is a nonuid mass containing at least 10% of fibrous material, and washing out the caustic alkali.

26'. A step in the method of producing puffed pulp by curling the libres thereof, this step consisting in impregnating the pulp with a caustic alkali solution of mercerizing strength, and maintaining the fluid content of the mass of pulp and solution such as to maintain a non-'Huido mass during the treatment.

JOSEPH E. PLUMSTEAD. 

